<template>
  <div>
    <div class="pagination">
      <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo--)">
        上一页
      </button>
      <button
        v-if="startNumAndEndNum.start > 1"
        @click="$emit('getPageNo', 1)"
        :class="{ active: pageNo == 1 }"
      >
        1
      </button>
      <button v-if="startNumAndEndNum.start > 2">···</button>
      <!-- 中间部分 -->
      <button
        v-for="(page, index) in startNumAndEndNum.end"
        :key="index"
        v-if="page >= startNumAndEndNum.start"
        @click="$emit('getPageNo', page)"
        :class="{ active: pageNo == page }"
      >
        {{ page }}
      </button>
      <!-- 下 -->
      <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
      <button
        v-if="startNumAndEndNum.end < totalPage"
        @click="$emit('getPageNo', totalPage)"
        :class="{ active: pageNo == totalPage }"
      >
        {{ totalPage }}
      </button>
      <button
        :disabled="pageNo == totalPage"
        @click="$emit('getPageNo', pageNo++)"
      >
        下一页
      </button>
      <button style="margin-left: 30px">共{{ total }}页</button>
    </div>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  // pageNo:当前第几个// pageSize:每一页展示的数据
  // total:整个分页器所有的数// continues:代表分页连续页码个数
  props: ["total", "pageSize", "pageNo", "continues"],
  computed: {
    //总共多少页
    totalPage() {
      // 向上取整
      return Math.ceil(this.total / this.pageSize);
    },
    // 计算出连续的页码的起始数字和结束数字
    startNumAndEndNum() {
      const { pageNo, continues, totalPage } = this;
      //先定义两个变量存储起始数字与结束数字
      let start = 0,
        end = 0;
      // 不正常现象[总页数没有连续页码多]
      if (continues > totalPage) {
        start = 1;
        end = totalPage;
      } else {
        //   正常现象[连续页码5,但是你的总页数一定是大于5的]
        // 起始数字
        start = pageNo - parseInt(continues / 2);
        // 结束数字
        end = pageNo + parseInt(continues / 2);
        // 当分页器起始数字出现0或负数，纠正他
        if (start < 1) {
          start = 1;
          end = continues;
        }
        // 当结束(终点)数字大于总页数,纠正他
        if (end > totalPage) {
          end = totalPage;
          start = totalPage - continues + 1;
        }
      }
      return { start, end };
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active {
  background-color: skyblue;
}
</style>
